SASS compiliation errors in latest version

Hi

Upgrading to version 3 of the NPM package is causing issues in our project. I'm getting these SASS errors:

```
ERROR in ./src/sass/main.scss (./node_modules/css-loader/dist/cjs.js!./node_modules/sass-loader/dist/cjs.js!./src/sass/main.scss)
Module build failed (from ./node_modules/sass-loader/dist/cjs.js):
SassError: Function hsl is missing argument $saturation.
on line 7 of /Users/sambrown/Local Sites/obpmulti/app/public/wp-content/themes/ob/src/sass/main.scss
>> background: hsl(0 0% 20% / 100%);
```

Downgrading to v2.2.2 fixes it - it looks like those rules used to use `hsla()` instead of `hsl()`. Changing the rules to `hsla()` does fix it.

Any idea what's going wrong here?

The failure is reported from the consumer's src/sass/main.scss and passes through css-loader and sass-loader. Reproduce the v3 build with the shown hsl declaration, then compare the behavior with v2.2.2 and inspect the package's Sass/CSS output and dependency compatibility. Done means the v3 package compiles the reported stylesheet without a consumer-side workaround.

Written by the indexing model from the issue text.